A direct-current-side bus voltage is equally divided between direct-current-side series capacitors of a single-phase converter in an ideal case. However, in an embodiment, due to factors such as a capacitance error or inconsistent characteristics of switch devices, there is a deviation between voltages of the capacitors on a direct-current-side bus. As a result, system neutral-point potential fluctuates. That is, the system neutral-point potential is unbalanced. When the system neutral-point potential is unbalanced, quality of an output waveform is affected, and a voltage stress on a specific switching transistor is increased, and the switching transistor is damaged in a severe case. Based on this, a single-phase converter control method is provided and includes obtaining a voltage vector of a single-phase alternating current system, obtaining another voltage vector orthogonal to the voltage vector through a time delay link, converting the two voltage vectors into three-phase modulated waves, generating, based on an existing Discontinuous Pulse Width Modulation (DPWM) method of a three-phase alternating current system, a common-mode component that needs to be injected into the three-phase modulated waves, performing superposition on an initial modulated wave of the single-phase system and the injected common-mode component, to generate a modulated wave, and controlling activation and an on/off state of a switch device based on the modulated wave. However, the time delay link in the foregoing single-phase converter control method increases a system delay, reduces a system response speed, and affects a system control feature. In addition, a single-phase two-level converter lacks a system neutral-point potential balancing capability.